Job-creation proposals are flying out of the White House like popcorn these days. Democrats in Congress need all the help they can get to retain power after the Nov. 2 elections. And President Obama is trying desperately to take the chill out of a frosty economy.

Of all the ideas that Mr. Obama has lately adopted to boost employment, one deserves a serious debate during the election campaign and on Capitol Hill: creation of an investment bank to raise private capital for the building of public roads, rail, and other transportation infrastructure.

Oddly, despite the political timing of Obama’s proposal just weeks before the election, such a bank would help remove some pork-barrel politics that now influence the construction of highways and mass transit. Projects would be decided on their merits by an independent board within an infrastructure bank – and for one simple reason. The bank would need to pay back its investors.

The concept isn’t new. Such private-public banks have long operated in other countries. They rely on seed money from government to attract private capital in the granting of loans for big projects that can spur economic growth or that can earn money from user fees.

Such a bank in the US would have a stronger incentive than Congress does now to make sure that a highway or a rail system is well maintained over time.